D 处少n吧吧多 G eo 四时L N 图5-8.海绵动物受精后的胚验发育 A.受精卵;B.8胚胞期;C,16胚胞期;D.8胚胞期;E、F,要胚期(切面);G.轻的小胚胞向囊粒内生 出鞭毛(切面);H、.大胚胞一端形成一个开孔,并向外包,里而的变成外面(鞭毛在小胚胞的表面)(切而)J.幼 两仁幼虫(切面);五,两囊幼虫;L,小胚内陷;M,固(纵切面),(集自 Storer垂 Usinger; Marshall williams修改)
海锦动物的体制和造金 海绵动物是多细胞动物中最原始的类群, 体制基本上是辐射对称,这种固着生活 对称的体制只有因着端和分离端之分,身 体周围是相似的。 这是一种对固着生活的适应。绝 大多数在海水中或淡水中营固着生活。 进化地位 发有海绵类群
Flavell ) the sea floor. (b) The sponge body plan. The black fringe in the body cavity represents nt FIGURE 22-6 Sponges. (a) These golden tubes are sponges, growing attached to coral flagella of collar cells, whose beating draws the feeding current through the body. Water en ters through numerous tiny openings on the sides and leaves through the opening at the to (arrows).(c) A collar cell, a type of cell characteristic of sponges. Lashing of the flagellum op drats a current of water through the collar, a ring of microvilli that trap food particles Food is ingested by endocytosis and digested intracellularly.(a, Alice Alldredge)
Water out tattered through Surface cell scutum central wafer in rough pores amoena 0 cellin semifluid matrox Figure 41.6 Morphology of a simple sponge (a) and a more compiex form(b) Purple shading indicates the location of collar cells, which trap bacteria and small food panicles on their cofar of microvilli Black arrows indicate the direction ot water tow througn the sponge, as caused by the collective beating of the Bagela of collar cells. (c) Small section through a sponge body wall
海绵动的遽瀚水 皮屐 扁平胞 海绵动物的体壁由两层细胞构成,中股层 外层称为皮层,是一层扁平细胞,里面 的一层称为胃层,由非细胞结构的领鞭 胃 毛细胞组成.皮层与胃层之间的部分是领鞭毛铷胞 中胶层,体壁包围的空腔为中夹腔 中央腔 出水孔 水孔一 谦化地位体制生发海绵类群